Image signal processing device, imaging device, flicker check method in imaging device, and server

ABSTRACT

This invention enables one to check flicker of a HFR image signal. A display image signal of a first frame rate for flicker check is obtained on the basis of an image signal of a second frame rate. For example, the display image signal of the first frame rate is generated from the image signal of the second frame rate by a frame thinning process. In this case, a frame to be thinned is determined from a relationship between the second frame rate and a light source frequency. For example, the number of frames to be a flicker period is obtained from the second frame rate and the light source frequency, and the frame to be thinned is determined so that continuous frames of the number of frames to be the flicker period are present. In addition, for example, for each predetermined frame, the frame to be thinned is determined so as to extract a frame of which a flicker phase sequentially changes.

TECHNICAL FIELD

The present technology relates to an image signal processing device, animaging device, a flicker check method in an imaging device, and aserver.

BACKGROUND ART

High frame rate cameras (HFR cameras) capable of imaging at a high framerate with a frame rate higher than a standard frame rate have becomewidespread. A slow motion effect can be easily obtained by using theimage signal obtained by imaging with an HFR camera. In photographingunder a light source such as a fluorescent lamp that blinks due to apower supply frequency, flicker occurs as a phenomenon generated from adifference between a light source period and an imaging period. Theflicker is more conspicuous especially in the HFR camera of which animaging rate is higher than the light source frequency. For example,Patent Literature 1 discloses a technology for correcting flicker.

An HFR camera generally has a monitor output for checking thebrightness, white balance, or the like of a picture being imaged in realtime. It is desirable for the picture displayed on the monitor to beoriginally capable of faithfully displaying the brightness or the whitebalance of the picture being imaged. In the related art, for example, itis known that a monitor output of a high-quality standard frame ratewith high S/N can be obtained by averaging in a frame direction, or amonitor output of a standard frame rate with high dynamic resolution canbe obtained by thinning in a frame direction.

However, with such a monitor output, it is not possible to accuratelycheck characteristic flicker in a captured image signal of the HFRcamera. Flicker is a luminance change phenomenon in frame unitsappearing in a case in which an image is captured under a blinking lightsource. In a monitor output of a frame addition method, a luminancedifference is lost by an addition, and the flicker is not able to becorrectly expressed. Similarly, in the monitor output of the thinningmethod, since the luminance difference is not a continuous framerelationship, the luminance difference that appears is not correct.

In the related art, by recording the captured image signal of the HFRcamera once on a recording medium and reproducing the captured imagesignal, the flicker is checked, and if necessary, a flicker correctionfunction is used. However, even when a flicker correction effect ischecked, it is necessary to record once and reproduce the captured imagesignal, and it takes time and effort for a user.

CITATION LIST Patent Literature

Patent Literature 1: JP 2009-135792A

DISCLOSURE OF INVENTION Technical Problem

The purpose of the present technology is to make it possible to easilycheck flicker of an HFR image signal.

Solution to Problem

A concept of the present technology resides in an imaging deviceincluding: an imaging unit configured to obtain an image signal of asecond frame rate higher than a first frame rate; and an image signalprocessing unit configured to generate a display image signal of thefirst frame rate by a frame thinning process from the image signal ofthe second frame rate. The image signal processing unit determines aframe to be thinned from a relationship between the second frame rateand a light source frequency.

In the present technology, an image signal of a second frame rate higherthan a first frame rate is able to be obtained by an imaging unit. Thefirst frame rate is, for example, a standard frame rate, such as 60 fps.On the other hand, the second frame rate is, for example, a high framerate and is 120 fps, 180 fps, 240 fps, or the like.

A display image signal of the first frame rate is generated from animage signal of the second frame rate by a frame thinning process, by animage signal processing unit. Here, a frame to be thinned is determinedfrom a relationship between the second frame rate and a light sourcefrequency. For example, the image signal processing unit may obtain thenumber of frames to be a flicker period from the second frame rate andthe light source frequency, and may determine the frame to be thinned sothat continuous frames of the number of frames to be the flicker periodare present.

In this case, for example, the number of frames to be the flicker periodmay be obtained from Math. “number of frames to be flicker period=LCM(light source frequency, second frame rate)/(light source frequency)”.LCM (Element 1, Element 2) indicates the least common multiple of“Element 1 and Element 2”. In addition, in this case, for example, thenumber of frames to be the flicker period may be obtained from Math.“number of frames to be flicker period=ROUND (second frame rate)/(lightsource frequency)”. ROUND (Element) indicates a rounded value of“Element”.

In addition, for example, the image signal processing unit may determinethe frame to be thinned so as to extract a frame of which a flickerphase sequentially changes, for each predetermined frame.

As described above, in the present technology, the frame to be thinnedis determined from the relationship between the second frame rate andthe light source frequency, and the display image signal of the firstframe rate is generated from the image signal of the second frame rateby the frame thinning process. Therefore, it is possible to leave aluminance difference of flicker in each frame of the display imagesignal of the first frame rate, and it is possible to check the flickerin real time by the display image signal of the first frame rate.

Note that, in the present technology, for example, the image signalprocessing unit may have a normal process mode and a flicker check mode,and when the image signal processing unit is in the flicker check mode,the image signal processing unit may generate the display image signalof the first frame rate from the image signal of the second frame rateby the frame thinning process, and determine the frame to be thinnedfrom the relationship between the second frame rate and the light sourcefrequency. In this case, the display image signal of the first framerate is able to check the flicker in real time by setting a flickercheck mode.

Note that, in the normal process mode, similarly to the related art, thedisplay image signal of the first frame rate is generated by averagingin a frame direction or thinning in the frame direction. In this case,the display image signal of the first frame rate is able to check thebrightness, a white balance, or the like of a captured image in realtime.

In this case, for example, a display control unit configured to displaythat the image signal processing unit is in the flicker check mode on adisplay unit that displays an image by the display image signal when theimage signal processing unit is in the flicker check mode may be furtherincluded. In this case, from display on a display unit (monitor), theuser is able to easily recognize that it is in a flicker check mode,that is, it is in a special monitor output mode.

In addition, in the present technology, for example, a flickercorrection unit configured to perform a flicker correction process onthe image signal of the second frame rate on the basis of the secondframe rate and the light source frequency may be further included. Theimage signal processing unit may generate the display image signal ofthe first frame rate from the image signal of the second frame rate ofwhich flicker is corrected. In this case, the display image signal ofthe first frame rate generated by an image signal processing unit isable to check flicker after flicker correction in a flicker correctionunit in real time.

In this case, for example, an operation unit for operating the flickercorrection process of the flicker correction unit may be furtherprovided. Therefore, the user is able to perform a change operation ofthe flicker correction process in the flicker correction unit asnecessary according to the flicker checked by the display image signalof the first frame rate.

In addition, another concept of the present technology resides in animaging device including: an imaging unit configured to obtain an imagesignal of a second frame rate higher than a first frame rate; an imagesignal processing unit configured to generate a display image signal ofthe first frame rate from the image signal of the second frame rate; aluminance level detection unit configured to detect a luminance level ofa frame of a predetermined number of continuous frames of the secondframe rate; and a signal superimposing unit configured to superimpose adisplay signal for displaying the detected luminance level of the frameof the predetermined number of frames on the display image signal.

In the present technology, an image signal of a second frame rate higherthan a first frame rate is able to be obtained by an imaging unit. Thefirst frame rate is, for example, a standard frame rate, such as 60 fps.On the other hand, the second frame rate is, for example, a high framerate and is 120 fps, 180 fps, 240 fps, or the like.

The display image signal of the first frame rate is generated from theimage signal of the second frame rate by the image signal processingunit. In this case, for example, a process of averaging the image signalof the second frame rate in the frame direction or a process of thinningthe image signal of the second frame rate in the frame direction isexecuted on the image signal of the second frame rate to generate thedisplay image signal of the first frame rate.

A luminance level of a frame of a predetermined number of continuousframes of the image signal of the second frame rate is detected by aluminance level detection unit. For example, the predetermined number offrames may be the number of frames to be a flicker period obtained fromthe second frame rate and the light source frequency. A display signalfor displaying the detected luminance level of the frame of thepredetermined number of frames is superimposed on the display imagesignal of the first frame rate by a signal superimposing unit.

As described above, in the present technology, the display signal fordisplaying the luminance level detected in the frame of thepredetermined number of continuous frames of the image signal of thesecond frame rate is superimposed on the display image signal of thefirst frame rate. Therefore, the luminance level detected in the frameof the predetermined number of frames is displayed on the imagedisplayed by the display image signal as, for example, a bar, anumerical value, or the like, and it is possible to check the flicker inreal time.

Another concept of the present technology resides in a server including:a recording and reproducing unit configured to record an input imagesignal of a second frame rate higher than a first frame rate in astorage and reproduce an output image signal from the storage; and aprocessing unit configured to obtain a display image signal of the firstframe rate for flicker check on the basis of the input image signal ofthe second frame rate.

In the present technology, a recording and reproducing unit records aninput image signal of a second frame rate higher than a first frame ratein a storage and reproduces an output image signal from the storage. Aprocessing unit obtains a display image signal of the first frame ratefor flicker check on the basis of the input image signal of the secondframe rate.

For example, the processing unit may generate the display image signalof the first frame rate from the input image signal of the second framerate by the frame thinning process and may determine the frame to bethinned from the relationship between the second frame rate and a lightsource frequency. In this case, for example, the processing unit mayobtain the number of frames to be a flicker period from the second framerate and the light source frequency, and may determine the frame to bethinned so that continuous frames of the number of frames to be theflicker period are present. In addition, in this case, for example, theprocessing unit may determine the frame to be thinned so as to extract aframe of which a flicker phase sequentially changes, for eachpredetermined frame.

In addition, for example, the processing unit may superimpose a displaysignal that displays a luminance level of a frame of a predeterminednumber of continuous frames of the image signal of the second frame rateon an image signal of the first frame rate generated from the inputimage signal of the second frame rate to generate the display imagesignal of the first frame rate. In this case, for example, thepredetermined number of frames is the number of frames to be a flickerperiod obtained from the second frame rate and a light source frequency.

As described above, in the present technology, the display image signalof the first frame rate for flicker check is obtained on the basis ofthe input image signal of the second frame rate. Therefore, it ispossible to easily check the flicker in the image signal of the secondframe rate.

Advantageous Effects of Invention

According to the present technology, it is possible to check flicker ofa captured image signal of an HFR camera in real time. Note that theeffects described in the present specification are merely examples andare not intended to be limiting, and there may be additional effects.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating an example of a configuration ofan imaging device according to an embodiment.

FIG. 2 is a block diagram illustrating an example of a configuration ofa flicker correction circuit in a signal correction circuit.

FIG. 3 is a diagram illustrating a specific example of weighted additiontype flicker correction.

FIG. 4 is a diagram illustrating an example of a weighting coefficientset stored in a nonvolatile memory of the imaging device.

FIG. 5 is a diagram illustrating an example of a UI screen for setting aflicker correction condition displayed on a finder.

FIG. 6 is a diagram illustrating an example of a finder display in acase of a normal process mode and a flicker check mode.

FIG. 7 is a diagram illustrating an example of a process (frame additionmethod) of a finder output generation unit in a case of the normalprocess mode.

FIG. 8 is a diagram illustrating an example of a process (thinningmethod) of the finder output generation unit in a case of the normalprocess mode.

FIG. 9 is a diagram illustrating an example of a process (first method)of the finder output generation unit in the flicker check mode.

FIG. 10 is a diagram illustrating an example of a process (secondmethod) of the finder output generation unit in the flicker check mode.

FIG. 11 is a diagram illustrating an example of a process (secondmethod) of the finder output generation unit in the flicker check mode.

FIG. 12 is a diagram illustrating an example of a process (third method)of the finder output generation unit in the flicker check mode.

FIG. 13 is a block diagram illustrating an example of a configuration ofa video system according to an embodiment.

FIG. 14 is a block diagram illustrating an example of a configuration ofa server.

FIG. 15 is a block diagram illustrating another example of theconfiguration of the server.

FIG. 16 is a block diagram illustrating another example of theconfiguration of the server.

MODE(S) FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment for implementing the present technology(hereinafter, referred to as “embodiment”) will be described. Note thatthe description will be given in the following sequence.

1. First Embodiment 2. Second Embodiment

3. Modified example

1. First Embodiment Example of Configuration of Imaging Device

FIG. 1 illustrates an example of a configuration of an imaging device 1as a first embodiment. The imaging device 1 includes a lens unit 10, animaging unit 20, a signal correction circuit 30, a knee gamma correctioncircuit 40, a finder output generation unit 50, a main line signalprocessing unit 60, a finder 70, an operation input unit 80, anonvolatile memory 90, and a central processing unit (CPU) 100.

The lens unit 10 includes a combination of a photographing lens or aplurality of lenses. The lens unit 10 collects light from a subject andforms an image on an imaging surface of the imaging unit 20. The imagingunit 20 includes, for example, an image sensor such as a complementarymetal oxide semiconductor (CMOS) image sensor or a charge coupled device(CCD) having an imaging surface on which pixels arranged in a matrix areprovided. The imaging unit 20 receives the light of the subject incidentthrough the lens unit 10 on the imaging surface and supplies an imagesignal of a high frame rate obtained by performing photoelectricconversion in pixel units to the signal correction circuit 30.

The signal correction circuit 30 performs various corrections on theimage signal generated by the imaging unit 20. The signal correctioncircuit 30 includes a defect correction circuit 31 and a flickercorrection circuit 32 (luminance correction circuit). The defectcorrection circuit 31 detects an image signal corresponding to aposition of a defective pixel in the imaging unit 20 and corrects theimage signal. The flicker correction circuit 32 removes flickergenerated in the image signal due to a difference between a power supplyfrequency and a frame rate. The signal correction circuit 30 suppliesthe corrected image signal to the knee gamma correction circuit 40.

The knee gamma correction circuit 40 performs knee correction and gammacorrection on the image signal supplied from the signal correctioncircuit 30 and supplies a result to the finder output generation unit 50and the main line signal processing unit 60.

The finder output generation unit 50 converts the image signal of thehigh frame rate supplied from the knee gamma correction circuit 40 intoan image signal for finder display at a standard frame rate, forexample, 60 fps, and supplies the image signal for finder display to thefinder 70. In this embodiment, the finder output generation unit 50includes a normal process mode and a flicker check mode. Switchingbetween the two modes is controlled by the CPU 100, for example, inresponse to an operation from an operation input unit 80 of a user.Details of a process in the finder output generation unit 50 will bedescribed later.

In addition, the finder output generation unit 50 generates display dataof a graphical user interface (GUI) for receiving an input of variouskinds of information from the user using the operation input unit 80,performs superimposition of the display data on a display image signal,or the like, and outputs the display data to the finder 70. The finder70 performs display of an image by the image signal obtained by thefinder output generation unit 50, display of the GUI by the display dataobtained by the finder output generation unit 50, and the like.

The main line signal processing unit 60 performs a process such ascompression coding and error correction coding on the image signal ofthe high frame rate supplied from the knee gamma correction circuit 40,and stores the processed image signal in a storage that is not shown ortransmits the processed image signal to an external device through atransmission cable.

For example, the operation input unit 80 receives input of settinginformation such as various photographing conditions from the user. Thenonvolatile memory 90 is, for example, a memory storing a plurality ofsets of weighting coefficients used in the flicker correction circuit32. The CPU 100 is a control circuit that performs overall control ofthe imaging device 1.

“Details of Flicker Correction Circuit”

FIG. 2 illustrates an example of a configuration of the flickercorrection circuit 32 in the signal correction circuit 30. The flickercorrection circuit 32 includes a memory controller 321, a memory 322,and a weighted addition circuit 323, and performs weighted addition typeflicker correction. Note that the weighted addition type flickercorrection method described here is an example, and the flickercorrection circuit 32 may perform flicker correction by a generalflicker correction method.

The flicker correction circuit 32 performs the flicker correction on theimage signal on the basis of the flicker correction condition given fromthe CPU 100. For example, the CPU 100 sets various correction conditionsand the like of the signal correction circuit 30 according to varioustypes of setting information input by the user using the operation inputunit 80 provided in the imaging device 1. The user is able to input thesetting information associated with the flicker correction. The settinginformation associated with the flicker correction includes a powersupply frequency, a frame rate, and an accumulation type (hereinafter,referred to as “ACM type”) that specifies a flicker correction mode.

Here, the setting information associated with the flicker correctionwill be described. For example, the power supply frequency has optionsof 50 Hz, 60 Hz, and the like. It is sufficient if the user selects asetting value of the power supply frequency according to a commercialpower supply frequency supplied to a region where the imaging device 1is used.

For example, the frame rate has options of 120 fps, 180 fps, 240 fps,480 fps, and the like. In a case in which the frame rate is twice thepower supply frequency, that is, lower than a light emission frequencyof a fluorescent lamp, it is possible to remove flicker by driving ashutter at the light emission frequency of the fluorescent lamp.However, in a case in which the frame rate is higher than twice thepower supply frequency (light emission frequency of the fluorescentlamp), it is impossible to remove the flicker by the shutter. Therefore,it is necessary to perform the flicker correction through a signalprocess by the flicker correction circuit 32.

The ACM type is information for designating a set of weightingcoefficients to be given to each of M frames on which weighted additionis to be performed for the flicker correction by the weighted additioncircuit 323. The CPU 100 determines the set of weighting coefficients onthe basis of the setting information input by the user by operating theoperation input unit 80 and sets each of the weighting coefficients inthe weighted addition circuit 323.

In addition, the CPU 100 also sets the number of frames stored in thememory 322 in the memory controller 321 on the basis of the settinginformation input by the user by operating the operation input unit 80.Under the control of the CPU 100, the memory controller 321 stores theimage signal that is corrected by a correction circuit of a precedingstage in the signal correction circuit 30 in the memory 322, reads theimage signal of M frames from the memory 322 when the image signal ofthe set M frames are stored in the memory 322, and supplies the imagesignal to the weighted addition circuit 323.

The memory 322 is a storage region where the image signal of at least Mframes, which is corrected by the correction circuit in the precedingstage in the signal correction circuit 30 is stored. The memory 322always stores a newly input image signal of at least M frames. Thenumber of frames stored in the memory 322 may be greater than M.

The weighted addition circuit 323 is a circuit that inputs the imagesignal of the M frames that are supplied continuously by reading theimage signal of the M frames from the memory 322 by the memorycontroller 321, executes a weighted addition and averaging on the imagesignal of the M frames using the weighting coefficients set by the CPU100, and generates a flicker correction image by the weighted additiontype flicker correction. Here, a value of M is an integer of 2 or morethat is set with an integer obtained by rounding a value obtained bydividing the frame rate by a light source frequency (power sourcefrequency×2) as an upper limit.

The weighted addition type flicker correction multiplies the imagesignal of the continuous M frames on which the weighted addition is tobe performed by the weighting coefficients individually set for theframes of each rank in the M frames, and sets a result obtained byperforming addition averaging on a result of the multiplication as aflicker correction result for an image signal of a reference frame inthe M frames. Here, the reference frame is, for example, a frame of apredetermined rank among the M frames that are continuously supplied tothe flicker correction circuit 32, for example, the last supplied frameor the like. In a case in which the last supplied frame is used as thereference frame, the M continuous frames on which the weighted additionis to be performed are the reference frame and (M−1) frames that arecontinuously supplied to the flicker correction circuit 32 temporallybefore the reference frame.

FIG. 3 illustrates a specific example of the weighted addition typeflicker correction. In this example, a value of M indicating the numberof frames on which the weighted addition is to be performed is 4, avalue of the weighting coefficients individually set in the frames ofeach rank in the M continuous frames in advance is “4”, “3”, “2”, and“1” from a side of the reference frame side. The values of the weightingcoefficients may be manually input by the user using the operation inputunit 80 in advance or may be stored in the nonvolatile memory 90 inadvance. Note that, as described above, a group of values of a pluralityof weighting coefficients associated with frames of each rank in the Mcontinuous frames is hereinafter referred to as “weighting coefficientset”.

Under the above conditions, the weighted addition circuit 323 operatesas follows. First, the weighted addition circuit 323 multiplies theimage signal of the reference frame by the weighting coefficient “4” togenerate a weighted image signal of the reference frame. In addition,the weighted addition circuit 323 multiplies an image signal of a frame(−1F) that is input immediately before the reference frame by theweighting coefficient “3” to generate a weighted image signal of theframe (−1F).

In addition, the weighted addition circuit 323 multiplies an imagesignal of a frame (−2F) that is input immediately before the frame (−1F)by the weighting coefficient “2” to generate a weighted image signal ofthe frame (−2F). In addition, the weighted addition circuit 323multiplies an image signal of a frame (−3F) that is input immediatelybefore the frame (−2F) by the weighting coefficient “1” to generate aweighted image signal of the frame (−3F).

Next, the weighted addition circuit 323 adds values for eachcorresponding pixel (at the same position) to the weighted image signalof the reference frame, the weighted image signal of the frame (−1F),the weighted image signal of the frame (−2F), and the weighted imagesignal of the frame (−3F), to generate a weighted addition image signalfor the M frames. In addition, the weighted addition circuit 323 dividesthe weighted addition image signal for the M frames by a sum of theweighting coefficients in the weighting coefficient set. This result isa flicker correction image for the image signal of the reference frame.

It is possible to prevent blurring of the entire moving image in theflicker correction image from becoming a uniform tendency, and it ispossible to obtain motion blur with more natural appearance, byperforming such weighted addition type flicker correction. In addition,as a distance from the moving image of the reference frame increases, adegree of blurring increases and it is possible to obtain motion blurwith more natural appearance by maximizing the value of the weightingcoefficient set for the reference frame among the values of theweighting coefficients individually set for the frames of each rank inthe M frames.

A difference in the values of each weighting coefficient in theweighting coefficient set also causes flicker component to remain in theflicker correction image. On the other hand, the appearance of themotion blur changes depending on various conditions such as size, color,and speed of the moving image. Therefore, in a case in which attentionis paid only to the appearance of the motion blur and the values of eachweighting coefficient in the weighting coefficient set are selected, insome cases, conspicuous flicker may remain in the flicker correctionimage.

Therefore, in this embodiment, the user is able to select the bestweighting coefficient set from a viewpoint of the motion blur and aflicker removal effect. FIG. 4 illustrates an example of the weightingcoefficient set stored in the nonvolatile memory 90 of the imagingdevice 1. In this example, the weighting coefficient set is able to beselected by three kinds of ACM types from “1” to “3”. In the example ofFIG. 4, a frame having of which a value of the weighting coefficientvalue is “0” does not have a weighted addition target as a result bymultiplying the image signal by “0”.

In FIG. 4, it is assumed that a total of three kinds of weightingcoefficient sets are able to be selected by the ACM type from “1” to “3”for one combination of the power supply frequency and the frame rate,but more kinds of weighting coefficient sets may be prepared. Note thatthe values of each weighting coefficient in the weighting coefficientset are determined for each combination of the power source frequencyand the frame rate.

In individual weighting coefficient set, it is assumed that the value ofthe weighting coefficient assigned to the reference frame is set as themaximum value. The value of the weighting coefficient of the (M−1)frames other than the reference frame is determined such that a value ofa weighting coefficient of a frame temporally separated from thereference frame is not greater than a value of a weighting coefficientof a frame temporally closer to the reference frame compared to theframe thereof.

In other words, for a plurality of frames having different distancesfrom the frame of the predetermined rank in the (M−1) frames other thanthe frame of the predetermined rank, the value of the weightingcoefficient set for the frame of which a distance is relatively long isset to be equal to or less than the value of the weighting coefficientset for the frame of which a distance is relatively short. Therefore, itis possible to suppress a degree of influence on the flicker correctionimage by a moving image component in the frame which is furthertemporarily distant from the reference frame, and it is possible toobtain motion blur with more natural appearance.

In addition, in a plurality of kinds of weighting coefficient setsselected by the ACM type, the weighting coefficient set of which the ACMtype is “1” has the highest intensity of the flicker correction, andtherefore the intensity that affects the appearance of the motion bluris the highest. The value of the weighting coefficient in the weightingcoefficient set is set so that the intensity gradually decreases as theACM type becomes “2” and “3”. Note that one of the weighting coefficientsets selected by the ACM type may have the same value of the weightingcoefficient.

FIG. 5 illustrates an example of a UI screen for setting a flickercorrection condition displayed on, for example, the finder 70. Thisexample shows a case in which the power supply frequency=50 Hz, theframe rate=120 fps, and the ACM type=1 are set as the flicker correctioncondition.

The power frequency, the frame rate, and the ACM type selected by theuser using the operation input unit 80 are given to the CPU 100. The CPU100 refers to the weighting coefficient set corresponding to thecombination of the power supply frequency, the frame rate, and the ACMtype given from the nonvolatile memory 90, and sets the values of theweighting coefficients for each frame of each rank in the weightingcoefficient set to the weighted addition circuit 323. Therefore, theweighted addition circuit 323 performs the flicker correction using theweighted addition by the set value of the weighting coefficient on theimage signal of the input continuous M frames.

The user checks the appearance of the motion blur in the flickercorrection image and the flicker removal effect obtained under theflicker correction condition set by the user with an image or the likedisplayed on the finder 70 by causing the finder output generation unit50 to be a flicker check mode. Thereafter, as necessary, the useroperates the operation input unit 80 or the like to set a next flickercorrection condition in which only the ACM type is changed, so as tocheck the flicker correction image obtained by executing the flickercorrection under the flicker correction condition.

The user repeats the change of the ACM type and the check of the flickercorrection image as described above, and determines the ACM type inwhich the appearance of the motion blur and the degree of the removal ofthe flicker component are the best. In many operation environments ofthe imaging device 1, while the power supply frequency and the framerate are determined, the user switches only the ACM type, checks theflicker correction image each time, and determines the best ACM type.

In the plurality of kinds of weighting coefficient sets selected by theACM type, the value of the weighting coefficient in the weightingcoefficient set is set so that the weighting coefficient set of whichthe ACM type is “1” has the highest intensity that affects theappearance of the motion blur and the intensity gradually decreases asthe ACM type becomes “2” and “3”.

The user is first able to check the flicker correction image in whichthe appearance of the motion blur has largely changed by selecting theweighting coefficient set of the ACM type “1”, and thereafter, the useris able to check the flicker correction image by sequentially selectingthe ACM type of “2” and “3”. Therefore, the user is able to sequentiallycheck the flicker correction image in which the change in the appearanceof the motion blur is reduced step by step, and confusion whendetermining an optimum weighting coefficient set hardly occurs.

Note that, here, in the order of ACM types of “1”, “2”, and “3”, thevalue of the weighting coefficient in the weighting coefficient set isset so that the intensity of the weighting coefficient set that affectsthe appearance of the motion blur becomes weaker. However, conversely,in order of the ACM types of “1”, “2”, and “3”, the value of theweighting coefficient in the weighting coefficient set may be set sothat the intensity of the weighting coefficient set that affects theappearance of the motion blur becomes stronger.

“Description of Finder Output Generation Unit”

As described above, the finder output generation unit 50 includes thenormal process mode and the flicker check mode. The switching betweenthese two modes is controlled by the CPU 100, for example, in responseto the operation from the operation input unit 80 of the user.

For example, when the finder output generation unit 50 is in the flickercheck mode, display data for displaying that the finder outputgeneration unit 50 is in the flicker check mode on the finder 70 iscreated, and superimposes the display data on the image signal.Therefore, in the image displayed on the finder 70, displaying that thefinder output generation unit 50 is in the flicker check mode ispresent, and the user is easily able to check that the finder outputgeneration unit 50 is in the flicker check mode.

For example, when FIG. 6(b) is a finder display image of the normalprocess mode, when the finder output generation unit 50 is in theflicker check mode, as shown in FIG. 6(a), a character “FC” indicatingflicker is blinkingly displayed on a finder display image. Note that,the display for clearly indicating that the finder output generationunit 50 is in the flicker check mode to the user is not limited to thisexample, and other aspects may be used. For example, a frame of aspecific color may be added to the finder display image.

The normal process mode will be described. When the finder outputgeneration unit 50 is set to be in the normal process mode, the finderoutput generation unit 50 generates the image signal of the standardframe rate for finder display by performing a conventionally well-knownframe addition method or thinning method on the input image signal ofthe high frame rate.

FIG. 7 illustrates an example of a process by the frame addition method.This example shows a case in which the frame rate of the input imagesignal is 180 fps and the power supply frequency is 60 Hz (the lightsource frequency is 120 Hz).

FIG. 7(a) illustrates the main line image signal corresponding to theinput image signal. The main line image signal is the image signal ofthe high frame rate of 180 fps, and the image signals of each frame arecontinuous such as A1, A2, A3, B1, B2, B3, C1, C2, C3, and . . . .

Flicker is present in the image signal of the high frame rate of 180 fpsdue to an influence of the light source by the light source frequency of120 Hz. Numbers of 1, 2, and 3 attached to A, B, C, and . . . correspondto three phases of the flicker. Note that brightness on the drawing ofeach frame indicates a difference in luminance level of each frame dueto the flicker.

FIG. 7(b) illustrates an image signal of the standard frame rate (60fps) for the finder display obtained by the frame addition method. Inthis case, addition-averaging is performed in each of three frames of“A1, A2, and A3”, “B1, B2, and B3”, “C1, C2, and C3”, and . . . , andthe image signal for finder display of each frame is generated.

In the image signal for finder display obtained by the frame additionmethod as described above, since the luminance difference of each framedue to the flicker is lost by the addition, a finder display image isnot able to express the flicker included in the main image signal.Conversely, it is possible to display an image in which the influence ofthe flicker is suppressed.

FIG. 8 illustrates an example of a process by the thinning method.Similarly to the example of FIG. 7, this example also shows a case inwhich the frame rate of the input image signal is 180 fps and the powersupply frequency is 60 Hz (the light source frequency is 120 Hz).

Similar to FIG. 7(a), FIG. 8(a) illustrates the main line image signalcorresponding to the input image signal. FIG. 8(b) illustrates the imagesignal of the standard frame rate (60 fps) for the finder displayobtained by the thinning method. In this case, from the three frames ofeach of “A1, A2, and A3”, “B1, B2, and B3”, “C1, C2, and C3”, and . . ., frames having the same flicker phase, in this example A2, B2, C2, and. . . are extracted, and each frame of the image signal for finderdisplay is generated.

In the image signal for finder display obtained by the thinning methodas described above, since frames having the same flicker phase areextracted, a finder display image is not able to express the flickerincluded in the main image signal. Conversely, it is possible to displayan image in which the influence of the flicker is suppressed.

Next, the flicker check mode will be described. When the finder outputgeneration unit 50 is set to be in the flicker check mode, the finderoutput generation unit 50 generates the image signal of the standardframe rate for the finder display by performing any of the followingfirst to third methods on the input image signal of the high frame rateso that it is possible to express the flicker included in the main lineimage signal.

“First Method”

In the first method, basically, the finder output generation unit 50performs a frame thinning process on the input image signal of the highframe rate (second frame rate) to generate the image signal of thestandard frame rate (first frame rate) for the finder display. Here, theframe to be thinned is determined from the relationship between theframe rate of the input image signal and the light source frequency thatis twice the power supply frequency.

In the first method, the number of frames to be a flicker period isobtained from the frame rate of the input image signal and the lightsource frequency that is twice the power supply frequency, and the frameto be thinned is determined so that the continuous frames of the numberof frames to be the flicker period are present.

Here, the number of frames to be the flicker period is able to beobtained from the following Math. (1). Here, LCM (Element 1, Element 2)indicates the least common multiple of “Element 1 and Element 2”.

Number of frames to be flicker period=LCM (light source frequency, framerate of input image signal)/(light source frequency)  (1)

FIG. 9 illustrates an example of a process by the first method. Thisexample shows a case in which the frame rate of the input image signalis 120 fps and the power supply frequency is 50 Hz (the light sourcefrequency is 100 Hz). In this case, the flicker is present due to theinfluence of the light source by the light source frequency of 120 Hz inthe input image signal of 120 fps, and the number of frames to be theflicker period is obtained as 6 from the above-described Math. (1).

FIG. 9(a) illustrates the main line image signal corresponding to theinput image signal. The main line image signal is the image signal ofthe high frame rate of 120 fps, and the image signals of each frame arecontinuous such as A1, A2, A3, A4, A5, A6, B1, B2, B3, B4, B5, B6, C1,C2, C3, C4, C5, C6, and . . . . Numbers of 1, 2, 3, 4, 5, and 6 attachedto A, B, C, and . . . correspond to six phases of the flicker. Note thatthe brightness on the drawing of each frame indicates the difference inluminance level of each frame due to the flicker.

FIG. 9(b) illustrates the image signal of the standard frame rate (60fps) for finder display obtained by the process according to the firstmethod. In this case, each of frames of A1 to A6, which is the number offrames to be the flicker period, is stored in the memory, and each offrames is sequentially read from the memory at the standard frame rate(60 fps) and is output.

The frames (frames B1 to B6) during the read from the memory asdescribed above are not stored in the memory and are thinned.Thereafter, each of frames of C1 to C6, which is the number of frames tobe the next flicker period, is stored in the memory, and each of framesis sequentially read from the memory at the standard frame rate (60 fps)and is output. Hereinafter, this is repeated, and each frame of theimage signal for finder display is generated.

As described above, the image signal for finder display obtained by thefirst method includes the frames which are continuous in phase of theflicker. Therefore, the flicker included in the main line image signalis expressed in the finder display image, and the degree of the flickerincluded in the main line image signal is able to be checked in realtime.

Note that it is theoretically possible to accurately obtain the numberof frames to be the flicker period from Math. (1). However, depending onthe relationship between the frame rate of the input image signal andthe light source frequency, since the number of frames to be the flickerperiod may become very large, a case in which it is not realistic from aviewpoint of a necessary memory capacity also may occur. For example,there are a case in which the frame rate of the input image signal is59.94 fps and the power supply frequency is 50 Hz (the light sourcefrequency is 100 Hz), and the like.

In such a case, the number of frames to be the flicker period may beobtained from the following Math. (2). Here, ROUND (Element) indicates avalue obtained by rounding “Element”. Number of frames to be flickerperiod=ROUND (frame rate of input image signal/light sourcefrequency)  (2)

For example, in a case in which the frame rate of the input image signalis 239.76 fps (=4×59.94 fps) and the power supply frequency is 60 Hz(the light source frequency is 120 Hz), the number of frames to be theflicker period is 2 by Math. (2). Even though the number of frames to bethe flicker period is obtained by using the Math. (2) instead of Math.(1), there are no practical problems in many cases.

“Second Method”

In the second method, basically, the finder output generation unit 50performs a frame thinning process on the input image signal of the highframe rate (second frame rate) to generate the image signal of thestandard frame rate (first frame rate) for the finder display. Here, theframe to be thinned is determined from the relationship between theframe rate of the input image signal and the light source frequency thatis twice the power supply frequency.

In the second method, when the frame rate of the input image signal is Ntimes the standard frame rate for finder display, the frame to bethinned is determined such that frames having different flicker phasesare extracted for each of N frames.

FIG. 10 illustrates an example of a process by the second method. Thisexample shows a case in which the frame rate of the input image signalis 180 fps and the power supply frequency is 60 Hz (the light sourcefrequency is 120 Hz). In this case, when the frame rate of the inputimage signal is 180 fps and the standard frame rate is 60 fps, N=3.Furthermore, in this case, the number of frames to be the flicker periodobtained by the above-described Math. (1) is 3, which is equal to thevalue of N.

FIG. 10(a) illustrates the main line image signal corresponding to theinput image signal. The main line image signal is the image signal ofthe high frame rate of 180 fps, and the image signals of each frame arecontinuous such as A1, A2, A3, B1, B2, B3, C1, C2, C3, D1, D2, D3 . . .and so on, wherein numbers of 1, 2, and 3 attached to A, B, C, D . . .and so on correspond to three phases of the flicker. Note that thebrightness on the drawing of each frame indicates the difference inluminance level of each frame due to the flicker.

FIG. 10(b) illustrates the image signal of the standard frame rate (60fps) for finder display obtained by the process according to the secondmethod. In this case, from the three frames of “A1, A2, and A3”, “B1,B2, and B3”, “C1, C2, and C3”, and . . . , frames in which the flickerphase sequentially changes, in this example, A3, B1, and C2, . . . areextracted, and each frame of the image signal for finder display isgenerated.

As described above, the image signal for finder display obtained by thesecond method includes the frames which are continuous in phase of theflicker. Therefore, the flicker included in the main line image signalis expressed in the finder display image, and the degree of the flickerincluded in the main line image signal is able to be checked in realtime.

Note that the existing high-speed imaging device has a mechanism thatonce stores a captured image signal of a high frame rate in a memory andoutputs frames of a double speed number in parallel. Only in a case inwhich the number of frames to be the flicker period is the same as theparallel number or less than the parallel number by one, it is possibleto realize the process of the second method by selecting the frame fromthe parallel output.

FIG. 11 illustrates another example of a process by the second method.This example shows a case in which the frame rate of the input imagesignal is 120 fps and the power supply frequency is 50 Hz (the lightsource frequency is 100 Hz). In this case, when the frame rate of theinput image signal is 120 fps and the standard frame rate is 60 fps,N=2. Furthermore, in this case, the number of frames to be the flickerperiod obtained by the above-described Math (1) is 6, which is not equalto the value of N.

FIG. 11(a) illustrates the main line image signal corresponding to theinput image signal. The main line image signal is the image signal ofthe high frame rate of 120 fps, and the image signals of each frame arecontinuous such as A1, A2, A3, A4, A5, A6, B1, B2, B3, B4, B5, B6, C1,C2, C3, C4, C5, C6 . . . and so on. Numbers of 1, 2, 3, 4, 5, and 6attached to A, B, C . . . and so on correspond to six phases of theflicker. Note that the brightness on the drawing of each frame indicatesthe difference in luminance level of each frame due to the flicker.

FIG. 11(b) illustrates the image signal of the standard frame rate (60fps) for finder display obtained by the process according to the secondmethod. In this case, from the two frames of “A1 and A2”, “A3 and A4”,“A5 and A6”, “B1 and B2” . . . and so on, frames in which the flickerphase sequentially changes, in this example, A1, A3, A5, B2 . . . and soon are extracted, and each frame of the image signal for finder displayis generated.

As described above, the image signal for finder display obtained by thesecond method includes the frames in which the phase of the flickersequentially changes. In this case, since the number of frames to be theflicker period is not equal to the value of N, the image signal forfinder display does not include the frames which are continuous in phaseof the flicker.

Therefore, in the finder display image, an approximate flicker includedin the main line image signal is expressed, and thus it is possible tocheck an approximate degree of the flicker included in the main lineimage signal in real time. That is, although it is not possible tocorrectly grasp the degree of the flicker included in the main lineimage signal, it is useful for comparatively grasping a degree ofeffectiveness of the flicker correction.

“Third Method”

In the third method, the finder output generation unit 50 generates theimage signal of the standard frame rate (first frame rate) for finderdisplay by performing a conventionally well-known frame addition methodor thinning method from the input image signal of the high frame rate(second frame rate).

In addition, the finder output generation unit 50 detects the luminancelevel of a predetermined number of continuous frames of the input imagesignal and superimposes a display signal indicating the luminancedetection level of the frame of the predetermined number of frames onthe image signal for finder display. For example, the predeterminednumber of frames is, for example, the number of frames to be the flickerperiod obtained by the above-described Math. (1) or (2).

Therefore, the luminance level detected in the frame of thepredetermined number of continuous frames is displayed on the image bythe image signal for finder display, for example, as a bar, a numericalvalue, or the like, and the user is able to check the degree of theflicker included in the main line image signal in real time.

FIG. 12 illustrates an example of a process by the third method. Thisexample shows a case in which the frame rate of the input image signalis 180 fps and the power supply frequency is 60 Hz (the light sourcefrequency is 120 Hz). The number of frames to be the flicker periodobtained by the above-described Math (1) is 3.

FIG. 12(a) illustrates the main line image signal corresponding to theinput image signal. The main line image signal is the image signal ofthe high frame rate of 180 fps, and the image signals of each frame arecontinuous such as A1, A2, A3, B1, B2, B3, C1, C2, C3, D1, D2, D3 . . .wherein numbers of 1, 2, and 3 attached to A, B, C, D . . . correspondto three phases of the flicker. Note that the brightness on the drawingof each frame indicates the difference in luminance level of each framedue to the flicker.

FIG. 12(b) illustrates the image signal of the standard frame rate (60fps) for finder display obtained by the process according to the thirdmethod. In this case, in each of three frames of “A1, A2, and A3”, “B1,B2, and B3”, “C1, C2, and C3”, and so on, addition or thinning isperformed by a conventionally well-known frame addition method orthinning method, and each frame of the image signal for finder displayis generated.

In addition, in each of the three frames, an integration value of allpixels is obtained as a value of the luminance level of each frame, anda display signal indicating the detection level is superimposed on theimage signal for finder display. Note that, in the shown example, thevalue of the luminance level of each frame is bar-displayed, but thevalue of the luminance level of each frame may be shown by a numericalvalue or the like.

As described above, in the third method, the display signal indicatingthe luminance detection level of the frame of the number of thepredetermined continuous frames, for example, the number of frames to bethe flicker period is superimposed on the image signal of the standardframe rate (first frame rate) for finder display generated by theconventionally well-known frame addition method or thinning method.Therefore, the luminance level detected in the frame of thepredetermined number of frames is displayed on the image by the imagesignal for finder display as, for example, a bar, a numerical value, orthe like. The user is able to check the degree of the flicker includedin the main line image signal in real time while checking theconventional brightness, white balance, or the like in real time by thedisplay image.

As described above, in the imaging device 1 shown in FIG. 1, it ispossible to check the degree of the flicker included in the main lineimage signal in real time by the display image of the finder 70 bysetting the finder output generation unit 50 to be in the flicker checkmode. Therefore, it is possible to check the effect of the flickercorrection by the flicker correction circuit 32, and as necessary, theuser is able to easily and appropriately adjust a flicker correctionintensity by changing the ACM type or the like from the operation inputunit 80.

2. Second Embodiment Example of Configuration of Video System

FIG. 13 illustrates an example of a configuration of a video system 500as a second embodiment. The video system 500 has a predetermined numberof camera systems including a camera and a camera control unit (CCU). Inthis embodiment, the video system 500 has two camera systems of a camerasystem including a camera 501A and a CCU 502A and a camera systemincluding a camera 501B and a CCU 502B. The CCUs 502A and 502B performan image creation process on a captured image signal of a high framerate from the cameras 501A and 501B.

In addition, the video system 500 has a server 521 that performsrecording and reproducing of an image file for replay reproduction andthe like. The file recorded in the server 521 also includes a file ofimage signals 503A and 503B of the high frame rate output from the CCUs502A and 502B. The image signals 503A and 503B of the high frame rateoutput from the CCUs 502A and 502B are transmitted as an SDI signal tothe server 521 through a switcher 525 that will be described later.

In this embodiment, the server 521 generates a display signal of astandard frame rate for flicker check on the basis of the image signal503 (503A and 503B) of the high frame rate. Here, similarly to thefinder output generation unit 50 in the above-described firstembodiment, the server 521 generates the display signal for the flickercheck by the “first method”, the “second method”, or the “third method”.

In the first method, the frame thinning process is performed on theimage signal of the high frame rate (second frame rate) to generate thedisplay image signal of the standard frame rate (first frame rate).Here, the frame to be thinned is determined from the relationshipbetween the frame rate of the input image signal and the light sourcefrequency that is twice the power supply frequency. That is, in thisfirst method, the number of frames to be the flicker period is obtainedfrom the frame rate of the image signal of the high frame rate (secondframe rate) of the input image signal and the light source frequencythat is twice the power frequency, and the frame to be thinned isdetermined such that the continuous frames of the number of frames to bethe corresponding flicker period are present (refer to FIG. 9).

The display image signal of the standard frame rate for checking theflicker obtained by the first method includes the frames which arecontinuous in phase of the flicker. Therefore, the flicker included inthe image signal of the high frame rate is expressed in the displayimage, and it becomes possible to easily check the degree of theflicker.

In addition, in the second method, the frame thinning process isperformed on the image signal of the high frame rate (second frame rate)to generate the display image signal of the standard frame rate (firstframe rate). Here, the frame to be thinned is determined from therelationship between the frame rate of the input image signal and thelight source frequency that is twice the power supply frequency. Thatis, in this second method, when the frame rate of the input image signalis N times the standard frame rate, the frame to be thinned isdetermined such that frames having different flicker phases areextracted for each of N frames (see FIGS. 10 and 11).

The display image signal of the standard frame rate for checking theflicker obtained by the second method includes the frames of which aflicker phase sequentially changes. Therefore, the flicker included inthe image signal of the high frame rate is expressed in the displayimage, and it becomes possible to easily check the degree of theflicker.

In addition, in the third method, the image signal of the standard framerate (first frame rate) is generated from the image signal of the highframe rate (second frame rate) by a well-known frame addition method orthinning method. In addition, the luminance level of the predeterminednumber of continuous frames of the image signal of the high frame rateis detected and the display signal indicating the luminance detectionlevel of the frame of the predetermined number of frames is superimposedon the image signal of the standard frame rate described above, so as togenerate the display image signal of the standard frame rate (refer toFIG. 12). For example, the predetermined number of frames is the numberof frames to be the flicker period obtained from the second frame rateand the light source frequency.

The display image signal of the standard frame rate for checking theflicker obtained by the third method is obtained by superimposing thedisplay signal indicating the luminance detection level of the frame ofthe predetermined number of frames. Therefore, the luminance leveldetected in the frame of the predetermined number of the continuousframes is displayed on the display image as, for example, a bar, anumerical value or the like, and the user is able to easily check thedegree of the flicker included in the image signal of the high framerate.

In addition, the video system 500 has a monitor 523 that receives thedisplay image signal of the standard frame rate for the flicker check asthe SDI signal and presents the display image for the flicker check toan operator of the server 521. Note that the monitor 523 may not onlypresent the display image for the flicker check but also may serve as amonitor for appropriately checking the image in the file recorded in thestorage.

In addition, the video system 500 has the switcher 525. The imagesignals 503A and 503B of the high frame rate obtained by the CCUs 502Aand 502B are input as the SDI signal to the switcher 525. In addition,an image signal 524 of a high frame rate 524 reproduced by the server521 is also input to the switcher 525 as the SDI signal.

The switcher 525 selectively extracts a predetermined image signal froman image signal of a high frame rate input from a plurality of inputapparatuses such as a camera system and the server 521 and outputs thepredetermined image signal as a main line signal 526 or mixes randomimage signals among the image signals of the high frame rate input fromthe plurality of input apparatuses and outputs the mixed random imagesignals as the main line signal 526.

“Configuration of Server”

FIG. 14 illustrates an example of a configuration of the server 521. Theserver 521 has an SDI input unit 531, an encoder 532, a memorycontroller 533, a storage 534, a decoder 535, an SDI output unit 536,and a changeover switch 537.

The SDI input unit 531 receives the image signal 503 of the high framerate as the SDI signal and extracts the image signal 503 of the highframe rate from the SDI signal thereof. Here, the image signal 503 ofthe high frame rate may be input by any of one system and multiplesystems. For example, in a case in which the image signal 503 of thehigh frame rate is an image signal of 180 fps, for example, the imagesignal 503 is supplied by an image signal of 180 fps of one system or animage signal of 60 fps of three systems.

The encoder 532 implements an encoding process by a compression formatof, for example XAVC or the like on the image signal of the high framerate obtained by the SDI input unit 531 to generate a file (recordingfile). The file generated by the encoder 532 is recorded in the storage534 and is reproduced under control of the memory controller 533. Thememory controller 533 configures a recording and reproducing unit.

In the normal output mode, the memory controller 533 reproduces theimage signal of the high frame rate from the storage 534 and outputs theimage signal of the high frame rate as it is. On the other hand, in theflicker check mode, the image signal of the high frame rate isreproduced from the storage 534, the image signal of the high frame rateis processed, and the display image signal of the standard frame ratefor the flicker check by the first method, the second method, or thethird method described above is output. The memory controller 533configures a recording and reproducing unit and configures a processingunit of the image signal.

The decoder 535 implements a decoding process on the image signal outputfrom the memory controller 533 to obtain an image signal of baseband.The SDI output unit 536 outputs the image signal obtained by the decoder535 as the SDI signal. In the normal output mode, the changeover switch537 is connected to a side a, and outputs the image signal (SDI signal)524 of the high frame rate obtained by the SDI output unit 536 as a mainline output. On the other hand, in the flicker check mode, thechangeover switch 537 is connected to a side b, and outputs the displayimage signal (SDI signal) 522 of the standard frame rate for the flickercheck obtained by the SDI output unit 536 as a flicker check output.

FIG. 15 illustrates another example of the configuration of the server521. In FIG. 15, parts corresponding to those in FIG. 14 are denoted bythe same reference numerals. The server 521 has an SDI input unit 531,an encoder 532, a memory controller 533, a storage 534, decoders 535 and538, and SDI output units 536 and 539.

The SDI input unit 531 receives the image signal 503 of the high framerate as the SDI signal and extracts the image signal 503 of the highframe rate from the SDI signal thereof. Here, the image signal 503 ofthe high frame rate may be input by any of one system and multiplesystems. For example, in a case in which the image signal 503 of thehigh frame rate is an image signal of 180 fps, for example, the imagesignal 503 is supplied by an image signal of 180 fps of one system or animage signal of 60 fps of three systems.

The encoder 532 implements an encoding process by a compression formatof, for example XAVC or the like on the image signal of the high framerate obtained by the SDI input unit 531 to generate a file (recordingfile). The file generated by the encoder 532 is recorded in the storage534 and is reproduced under control of the memory controller 533. Thememory controller 533 configures a recording and reproducing unit.

The memory controller 533 reproduces the image signal of the high framerate from the storage 534 and outputs the image signal of the high framerate as it is. The decoder 535 implements a decoding process on theimage signal output from the memory controller 533 to obtain an imagesignal of baseband. The SDI output unit 536 sets the image signal of thehigh frame rate obtained by the decoder 535 as the SDI signal andoutputs the image signal (SDI signal) 524 of this high frame rate as amain line.

In addition, the memory controller 533 reproduces the image signal ofthe high frame rate from the storage 534, further processes the imagesignal of the high frame rate, and outputs the display image signal ofthe standard frame rate for the flicker check by the first method, thesecond method, or the third method described above. The memorycontroller 533 configures a recording and reproducing unit andconfigures a processing unit of the image signal.

The decoder 538 implements a decoding process on the display imagesignal of the standard frame rate output from the memory controller 533to obtain an image signal of baseband. The SDI output unit 539 outputsthe display image signal (SDI signal) 522 as a flicker check output byusing the display image signal of the standard frame rate obtained bythe decoder 538 as the SDI signal.

FIG. 16 illustrates still another example of the configuration of theserver 521. In FIG. 16, parts corresponding to those in FIG. 15 aredenoted by the same reference numerals. The server 521 has an SDI inputunit 531, an encoder 532, a memory controller 533, a storage 534, adecoder 535, SDI output units 536 and 539, and a processing unit 541.

The SDI input unit 531 receives the image signal 503 of the high framerate as the SDI signal and extracts the image signal 503 of the highframe rate from the SDI signal thereof. Here, the image signal 503 ofthe high frame rate may be input by any of one system and multiplesystems. For example, in a case in which the image signal 503 of thehigh frame rate is an image signal of 180 fps, for example, the imagesignal 503 is supplied by an image signal of 180 fps of one system or animage signal of 60 fps of three systems.

The encoder 532 implements an encoding process by a compression formatof, for example XAVC or the like on the image signal of the high framerate obtained by the SDI input unit 531 to generate a file (recordingfile). The file generated by the encoder 532 is recorded in the storage534 and is reproduced under control of the memory controller 533. Thememory controller 533 configures a recording and reproducing unit.

The memory controller 533 reproduces the image signal of the high framerate from the storage 534 and outputs the image signal of the high framerate as it is. The decoder 535 implements a decoding process on theimage signal output from the memory controller 533 to obtain an imagesignal of baseband. The SDI output unit 536 sets the image signal of thehigh frame rate obtained by the decoder 535 as the SDI signal andoutputs the image signal (SDI signal) 524 of this high frame rate as amain line.

The processing unit 541 processes the image signal of the high framerate obtained by the SDI input unit 531 and outputs the display imagesignal of the standard frame rate for the flicker check by the firstmethod, the second method, or the third method described above. The SDIoutput unit 539 outputs the display image signal (SDI signal) 522 as aflicker check output by using the display image signal of the standardframe rate obtained by the processing unit 541 as the SDI signal.

As described above, in the video system 500 shown in FIG. 13, thedisplay signal of the standard frame rate for the flicker check isgenerated on the basis of image signal 503 (503A and 503B) of the highframe rate, and the display image for the flicker check is presented onthe monitor 523, by the server 521. Therefore, the operator of theserver is able to easily check the degree of the flicker included in theimage signal of the high frame rate. Note that, in the abovedescription, it is assumed that an interface of the server 521 is theSDI. However, the interface of the server 521 is not limited to the SDI,and other interfaces for exchanging a general image signal is also ableto be considered.

3. Modified Example

Note that, in the above-described embodiment, an example in which thepresent technology is applied to the imaging device 1 (refer to FIG. 1)or the server 521 (refer to FIG. 13) and the degree of the flickerincluded in the image signal of the high frame rate is checked is shown.However, a configuration in which the processing unit (processingcircuit) that generates the display image signal of the standard framerate for the flicker check in the present technology is included in theCCUs 502 and 512 or the switcher 525 is also able to be considered. Inaddition, for example, in a case in which the video system 500 of FIG.13 has a configuration in which a baseband processor unit (BPU) isdisposed between the cameras 501A and 501B and the CCUs 502A and 502B, aconfiguration in which the processing unit (processing circuit) thatgenerates the display image signal of the standard frame rate for theflicker check is provided is also able to be considered.

In addition, in the above-described embodiment, an example in which animaging rate is an integral multiple of the standard frame rate isshown, but the present technology is also able to be applied to a casein which the imaging frame rate is not an integral multiple of thestandard frame rate.

Additionally, the present technology may also be configured as below.

(1)

An image signal processing device including:

an image signal processing unit configured to generate a display imagesignal of a first frame rate from an image signal of a second frame ratehigher than the first frame rate,

in which the image signal processing unit generates the display imagesignal of the first frame rate from the image signal of the second framerate by a frame thinning process and determines a frame to be thinnedfrom a relationship between the second frame rate and a light sourcefrequency.

(2)

The image signal processing device according to (1), in which the imagesignal processing unit obtains the number of frames to be a flickerperiod from the second frame rate and the light source frequency, anddetermines the frame to be thinned so that continuous frames of thenumber of frames to be the flicker period are present.

(3)

The image signal processing device according to (2), in which the numberof frames to be the flicker period is obtained from Math. number offrames to be flicker period=LCM (light source frequency, second framerate)/(light source frequency).

(4)

The image signal processing device according to (2), in which the numberof frames to be the flicker period is obtained from Math. number offrames to be flicker period=ROUND (second frame rate)/(light sourcefrequency).

(5)

The image signal processing device according to (1), in which the imagesignal processing unit determines the frame to be thinned so as toextract a frame of which a flicker phase sequentially changes, for eachpredetermined frame.

(6)

The image signal processing device according to any of (1) to (5), inwhich the image signal processing unit has a normal process mode and aflicker check mode, and when the image signal processing unit is in theflicker check mode, the image signal processing unit generates thedisplay image signal of the first frame rate from the image signal ofthe second frame rate by the frame thinning process, and determines theframe to be thinned from the relationship between the second frame rateand the light source frequency.

(7)

An image signal processing method including:

an imaging unit configured to obtain an image signal of a second framerate higher than a first frame rate; and

an image signal processing step of generating a display image signal ofa first frame rate by a frame thinning process from an image signal of asecond frame rate higher than the first frame rate,

in which, in the image signal processing step, a frame to be thinned isdetermined from a relationship between the second frame rate and a lightsource frequency.

(8)

An imaging device including:

an imaging unit configured to obtain an image signal of a second framerate higher than a first frame rate; and

an image signal processing unit configured to generate a display imagesignal of the first frame rate by a frame thinning process from theimage signal of the second frame rate,

in which the image signal processing unit determines a frame to bethinned from a relationship between the second frame rate and a lightsource frequency.

(9)

The imaging device according to (8), in which the image signalprocessing unit obtains the number of frames to be a flicker period fromthe second frame rate and the light source frequency, and sets the frameto be thinned so that continuous frames of the number of frames to bethe flicker period are present.

(10)

The imaging device according to (8), in which the image signalprocessing unit determines the frame to be thinned so as to extract aframe of which a flicker phase sequentially changes, for eachpredetermined frame.

(11)

The imaging device according to any of (8) to (10), in which the imagesignal processing unit has a normal process mode and a flicker checkmode, and when the image signal processing unit is in the flicker checkmode, the image signal processing unit generates the display imagesignal of the first frame rate from the image signal of the second framerate by the frame thinning process, and determines the frame to bethinned from the relationship between the second frame rate and thelight source frequency.

(12)

The imaging device according to (11), further including:

a display control unit configured to display that the image signalprocessing unit is in the flicker check mode on a display unit thatdisplays an image by the display image signal when the image signalprocessing unit is in the flicker check mode.

(13)

The imaging device according to any of (8) to (12), further including:

a flicker correction unit configured to perform a flicker correctionprocess on the image signal of the second frame rate on the basis of thesecond frame rate and the light source frequency,

in which the image signal processing unit generates the display imagesignal of the first frame rate from the image signal of the second framerate of which flicker is corrected.

(14)

The imaging device according to (13), further including:

an operation unit configured to operate the flicker correction processof the flicker correction unit.

(15)

A flicker check method in an imaging device including an imaging unitconfigured to obtain an image signal of a second frame rate higher thana first frame rate, the flicker check method including:

an image signal process step of generating a display image signal of thefirst frame rate by a frame thinning process from the image signal ofthe second frame rate, by an image signal processing unit; and

a display control step of displaying an image by the display imagesignal of the first frame rate on a display unit, by a display controlunit,

in which, in the image signal process step, a frame to be thinned isdetermined from a relationship between the second frame rate and a lightsource frequency.

(16)

An image signal processing device including:

an image signal processing unit configured to generate a display imagesignal of a first frame rate from an image signal of a second frame ratehigher than the first frame rate;

a luminance level detection unit configured to detect a luminance levelof a frame of a predetermined number of continuous frames of the imagesignal of the second frame rate;

a signal superimposing unit configured to superimpose a display signalfor displaying the detected luminance level of the frame of thepredetermined number of frames on the display image signal.

(17)

The image signal processing device according to (16), in which thepredetermined number of frames is the number of frames to be a flickerperiod obtained from the second frame rate and a light source frequency.

(18)

An image signal processing method including:

an image signal processing step of generating a display image signal ofa first frame rate from an image signal of a second frame rate higherthan the first frame rate, by an image signal processing unit;

a luminance level detection step of detecting a luminance level of aframe of a predetermined number of continuous frames of the second framerate, by a luminance level detection unit; and

a signal superimposing step of superimposing a display signal forindicating the detected luminance level of the frame of thepredetermined number of frames on the display image signal, by a signalsuperimposing unit.

(19)

An imaging device including:

an imaging unit configured to obtain an image signal of a second framerate higher than a first frame rate;

an image signal processing unit configured to generate a display imagesignal of the first frame rate from the image signal of the second framerate;

a luminance level detection unit configured to detect a luminance levelof a frame of a predetermined number of continuous frames of the imagesignal of the second frame rate; and

a signal superimposing unit configured to superimpose a display signalfor displaying the detected luminance level of the frame of thepredetermined number of frames on the display image signal.

(20)

A server including:

a recording and reproducing unit configured to record an input imagesignal of a second frame rate higher than a first frame rate in astorage and reproduce an output image signal from the storage; and

a processing unit configured to obtain a display image signal of thefirst frame rate for flicker check on the basis of the input imagesignal of the second frame rate.

(21)

The server according to (20), in which the processing unit generates thedisplay image signal of the first frame rate from the input image signalof the second frame, by a frame thinning process, and determines a frameto be thinned from a relationship between the second frame rate and alight source frequency.

(22)

The server according to (21), in which the processing unit obtains thenumber of frames to be a flicker period from the second frame rate andthe light source frequency, and determines the frame to be thinned sothat continuous frames of the number of frames to be the flicker periodare present.

(23)

The server according to (21), in which the processing unit determinesthe frame to be thinned so as to extract a frame of which a flickerphase sequentially changes, for each predetermined frame.

(24)

The server according to (20), in which the processing unit superimposesa display signal that displays a luminance level of a frame of apredetermined number of continuous frames of the image signal of thesecond frame rate on an image signal of the first frame rate generatedfrom the input image signal of the second frame rate to generate thedisplay image signal of the first frame rate.

(25)

The server according to (24), in which the predetermined number offrames is the number of frames to be a flicker period obtained from thesecond frame rate and a light source frequency.

REFERENCE SIGNS LIST

-   1 imaging device-   10 lens unit-   20 imaging unit-   30 signal correction circuit-   31 defect correction circuit-   32 flicker correction circuit-   40 knee gamma correction circuit-   50 finder output generation unit-   60 main line signal processing unit-   70 viewfinder-   80 operation input unit-   90 non-volatile memory-   100 CPU-   321 memory controller-   322 memory-   323 weighted addition circuit-   500 video system-   501A, 501B camera-   502A, 502B CCU-   521 server-   523 monitor-   525 switcher-   531 SDI input unit-   532 encoder-   533 memory controller-   534 storage-   535, 538 decoder-   536, 539 SDI output unit-   537 changeover switch-   541 processing unit

1. An image signal processing device comprising: an image signalprocessing unit configured to generate a display image signal of a firstframe rate from an image signal of a second frame rate higher than thefirst frame rate, wherein the image signal processing unit generates thedisplay image signal of the first frame rate from the image signal ofthe second frame rate by a frame thinning process and determines a frameto be thinned from a relationship between the second frame rate and alight source frequency.
 2. The image signal processing device accordingto claim 1, wherein the image signal processing unit obtains a number offrames to be a flicker period from the second frame rate and the lightsource frequency, and determines the frame to be thinned so thatcontinuous frames of the number of frames to be the flicker period arepresent.
 3. The image signal processing device according to claim 2,wherein the number of frames to be the flicker period is obtained fromMath. number of frames to be flicker period=LCM (light source frequency,second frame rate)/(light source frequency).
 4. The image signalprocessing device according to claim 2, wherein the number of frames tobe the flicker period is obtained from Math. number of frames to beflicker period=ROUND (second frame rate)/(light source frequency). 5.The image signal processing device according to claim 1, wherein theimage signal processing unit determines the frame to be thinned so as toextract a frame of which a flicker phase sequentially changes, for eachpredetermined frame.
 6. The image signal processing device according toclaim 1, wherein the image signal processing unit has a normal processmode and a flicker check mode, and when the image signal processing unitis in the flicker check mode, the image signal processing unit generatesthe display image signal of the first frame rate from the image signalof the second frame rate by the frame thinning process, and determinesthe frame to be thinned from the relationship between the second framerate and the light source frequency.
 7. An imaging device comprising: animaging unit configured to obtain an image signal of a second frame ratehigher than a first frame rate; and an image signal processing unitconfigured to generate a display image signal of the first frame rate bya frame thinning process from the image signal of the second frame rate,wherein the image signal processing unit determines a frame to bethinned from a relationship between the second frame rate and a lightsource frequency.
 8. The imaging device according to claim 7, whereinthe image signal processing unit obtains a number of frames to be aflicker period from the second frame rate and the light sourcefrequency, and sets the frame to be thinned so that continuous frames ofthe number of frames to be the flicker period are present.
 9. Theimaging device according to claim 7, wherein the image signal processingunit determines the frame to be thinned so as to extract a frame ofwhich a flicker phase sequentially changes, for each predeterminedframe.
 10. The imaging device according to claim 7, wherein the imagesignal processing unit has a normal process mode and a flicker checkmode, and when the image signal processing unit is in the flicker checkmode, the image signal processing unit generates the display imagesignal of the first frame rate from the image signal of the second framerate by the frame thinning process, and determines the frame to bethinned from the relationship between the second frame rate and thelight source frequency.
 11. The imaging device according to claim 10,further comprising: a display control unit configured to display thatthe image signal processing unit is in the flicker check mode on adisplay unit that displays an image by the display image signal when theimage signal processing unit is in the flicker check mode.
 12. Theimaging device according to claim 7, further comprising: a flickercorrection unit configured to perform a flicker correction process onthe image signal of the second frame rate on a basis of the second framerate and the light source frequency, wherein the image signal processingunit generates the display image signal of the first frame rate from theimage signal of the second frame rate of which flicker is corrected. 13.The imaging device according to claim 12, further comprising: anoperation unit configured to operate the flicker correction process ofthe flicker correction unit.
 14. A flicker check method in an imagingdevice including an imaging unit configured to obtain an image signal ofa second frame rate higher than a first frame rate, the flicker checkmethod comprising: an image signal process step of generating a displayimage signal of the first frame rate by a frame thinning process fromthe image signal of the second frame rate, by an image signal processingunit; and a display control step of displaying an image by the displayimage signal of the first frame rate on a display unit, by a displaycontrol unit, wherein, in the image signal process step, a frame to bethinned is determined from a relationship between the second frame rateand a light source frequency.
 15. An image signal processing devicecomprising: an image signal processing unit configured to generate adisplay image signal of a first frame rate from an image signal of asecond frame rate higher than the first frame rate; a luminance leveldetection unit configured to detect a luminance level of a frame of apredetermined number of continuous frames of the image signal of thesecond frame rate; and a signal superimposing unit configured tosuperimpose a display signal for displaying the detected luminance levelof the frame of the predetermined number of frames on the display imagesignal.
 16. The image signal processing device according to claim 15,wherein the predetermined number of frames is a number of frames to be aflicker period obtained from the second frame rate and a light sourcefrequency.
 17. A server comprising: a recording and reproducing unitconfigured to record an input image signal of a second frame rate higherthan a first frame rate in a storage and reproduce an output imagesignal from the storage; and a processing unit configured to obtain adisplay image signal of the first frame rate for flicker check on abasis of the input image signal of the second frame rate.
 18. The serveraccording to claim 17, wherein the processing unit generates the displayimage signal of the first frame rate from the input image signal of thesecond frame, by a frame thinning process, and determines a frame to bethinned from a relationship between the second frame rate and a lightsource frequency.
 19. The server according to claim 18, wherein theprocessing unit obtains a number of frames to be a flicker period fromthe second frame rate and the light source frequency, and determines theframe to be thinned so that continuous frames of the number of frames tobe the flicker period are present.
 20. The server according to claim 18,wherein the processing unit determines the frame to be thinned so as toextract a frame of which a flicker phase sequentially changes, for eachpredetermined frame.
 21. The server according to claim 17, wherein theprocessing unit superimposes a display signal that displays a luminancelevel of a frame of a predetermined number of continuous frames of theimage signal of the second frame rate on an image signal of the firstframe rate generated from the input image signal of the second framerate to generate the display image signal of the first frame rate. 22.The server according to claim 21, wherein the predetermined number offrames is a number of frames to be a flicker period obtained from thesecond frame rate and a light source frequency.